Monitoring the presence of corrosive ions is routinely done in the semiconductor and power industries. For detecting trace ions in ultra pure water (UPW) a large volume of the sample stream is concentrated into a concentrator column for further analysis. Typically an external sample stream pump is used to dispense the sample and route it through the concentrator column. These sample pumps typically are low cost and do not provide good flow control, resulting in variances in peak response and subsequently poor quantitation. Another potential problem is deterioration of the pump components due to their exposure to the sample stream. Also, changing sample streams can lead to contamination due to carry over. It would be useful to provide a low cost solution to the above problems.
The sample loop size in IC applications are chosen based on the required detection sensitivity for the ions of interest. Larger loops are typically used to detect low ppb level of ions. In some cases, the sample concentrations vary so much that there is a need to switch from a small loop size (e.g., ppm level of ions) to a larger loop size (e.g., ppb level of ions). With current instrumentation it is cumbersome to replace the loops and this is typically done manually.
From an operation perspective, mixing the sample zone with the eluent should be minimized to avoid poor peak shapes for the early eluting peaks, particularly while using large loop injection. It would be useful to have a method that would allow for sensitive detection of analytes of interest without changing the sample loop size.
It can be cumbersome to make large volume loops that are substantially stable under the high pressure requirements of the IC system. For a selected volume, the length of the tube increases with decreasing inner diameter of the sample loop tubing and the pressure rating decreases when the diameter of the tubing increases substantially.
In other applications with a large sample loop size, the void volume due to the large loop injection may result in a large baseline upset from the void and this affects the baseline integration of peaks eluting close to the void. For loop sizes significantly larger than the column volume, the large volume of unretained components such as water that traverse the entire column can cause problems of equilibration within the column and lead to undesirable baseline shifts and wander. This can lead to inaccuracies in peak integration and quantitation. It would be useful to eliminate the above discussed effects of large loop injections.
In neutralization applications, the sample slug is passed into the neutralizer device following which the neutralized sample is diverted into a concentrator column. A pump is used in the above application for the purpose of pumping a DI water stream that carries the sample slug through the neutralizer and for subsequent pre-concentration. The above setup requires an additional pump and suffers from some of the limitations discussed above. It would be useful to eliminate this additional sample stream pump and reduce the overall cost of the IC system.
Another area of sample preparation is matrix ion removal. Frequently with environmental samples, the analyte of interest is overwhelmed by matrix ions, and it is difficult to get good quantitative information. Under these conditions, a matrix ion elimination step may be needed. Similar to the neutralization application discussed above, a DI water pump is used to load the sample and divert it through a matrix ion elimination column and subsequently load the sample onto a concentrator column.
It would be useful to reduce the overall cost of an IC system.
Another area of sample preparation is in converting the sample to various forms prior to analysis. Similar to the above discussed applications this setup may also require a DI water pump. Here again it would be useful to reduce the overall cost of an IC system by eliminating the need for this pump.